A crawler type travelling body and a wheel type travelling body disclosed in JP2006-341732A are each known as a travelling body of a power shovel.
In a power shovel including the crawler type travelling body, fluid pressure motors are connected to respective crawlers arranged on both sides of the power shovel. These fluid pressure motors independently drive the respective crawlers.
In a power shovel including the wheel type travelling body, fluid pressure motors are connected to respective drive wheels arranged on both sides of the power shovel. These fluid pressure motors independently drive the respective drive wheels.
A fluid pressure circuit of each of the power shovels includes a first pump and a second pump. The first pump and the second pump are connected to a first circuit system and a second circuit system, respectively. One fluid pressure motor is connected to the first pump through a drive control valve arranged in the first circuit system, whereas the other fluid pressure motor is connected to the second pump through a drive control valve arranged in the second circuit system.
The power shovel with the crawler travelling body includes a travel control valve. When the power shovel is travelling in a straight line, flow paths are switched by the travel control valve to connect the two fluid pressure motors in parallel with respect to the first pump. This enables the two fluid pressure motors to be driven by one pump, thereby preventing a pressure difference between the fluid pressure motors.
The power shovel with the wheel type travelling body also includes a travel control valve. This travel control valve throttles a passage connecting the first pump and the first circuit system, and connects the second pump and the second circuit system without throttling. This prevents a pressure difference between the fluid pressure motors due to a shortage of the pressure fluid supplied to the fluid pressure motor of the first circuit system, the pressure fluid shortage being caused by driving a large-load actuator arranged in the first circuit system.